Having caused a stir in the German and mid-European papers, the news of Nobel laureate Günter Grass's membership of the Waffen-SS, the elite active-military wing of Hitler's infamous instrument of power, has been greeted by more of a whimper in their English-speaking equivalents.

Following the revelation in an interview with the Frankfurt Allgemeine Zeitung last Friday, responses in Germany have ranged between furious demands for the author to return his Nobel Prize to (very mild) expressions of sympathy and understanding. In the English-speaking press, the weekend saw the story relegated to the third entry in the "arts in brief" section of the New York Times and a minor placing in the Observer's celebrity gossip slot, "Good week, bad week" (where Grass is thought to have had a good week on the grounds of having got a load off his chest). Only the Sunday Times thought fit to run a major article.

There are, of course, good reasons for this comparative lack of interest, not least among them the media being busy with wars rather more recent than that in which Grass fought. Also, despite his genuinely international reputation, Grass's literary and political landscape is peculiarly and powerfully national, firmly rooted in the psychology of a country rebuilding itself in the aftermath of a shameful war. Perhaps, too, the issues raised by Grass's revelation seem less pressing because, in Britain at least, we don't really have characters like Grass. Uniformly respected if not necessarily universally admired by the intelligentsia, establishment and media alike, you'd need to imagine a kind of combination of, say, Harold Pinter, Tony Benn and Eric Hobsbawm to capture the image.

In Germany, by contrast, the furore is centred around the damaged credibility of a writer and commentator of almost unrivalled political and popular influence, foremost among whose political and literary themes has been modern Germany's problematic relation to the Third Reich and the need for complete honesty in the post-war project of reconstructing Germany's national and moral identity. And this is a difficult issue to negotiate.

The major charge levelled by the German commentariat is one of hypocrisy. It's understandable, for most people, that keeping quiet about being transferred at the age of 17 to a division of the Waffen-SS (already at some remove from the regular SS in ideological terms) in late 1944 amid the increasing chaos of the Eastern front hardly constitutes a criminal act. But for the self-appointed psychotherapist of a nation's collective consciousness to have so spectacularly failed to swallow the pill he has himself been prescribing with such confidence over the past 65 years - the sense of betrayal must be overwhelming.

There's no doubt that Grass, who has presented himself as a kind of moral exemplar whose outbursts, often judicious and occasionally opportunistic, were partly to be measured by the standard of his own personal integrity, is guilty of fairly gross hypocrisy. His pompous condemnation of Reagan and Köhl's landmark visit to the Bitburg cemetery near the Belgian border, on the grounds that Waffen-SS soldiers were buried there alongside regular German and US troops, now seems almost unbelievable.

As if this wasn't enough, there's also a clear sense that the way in which the revelation has emerged shortly before the publication of Grass's autobiography (he declined to mention the matter to his most recent biographer, Michael Jürgs) smacks of the worst kind of opportunism. As the historian Joachim Fest Grass put it, "I would no longer buy even a used car from this man".

The uproar and sense of betrayal in Germany is, then, wholly understandable. But, beyond Germany, to what extent should the revelations affect the author's national and international legacy?

Gossip value aside, Grass's membership of the 10th SS Panzer Division mainly raises for us the question of whether the revelation should make any difference to our reading of his work. The question would be easier, perhaps, if Grass were to have been revealed as a serious, unrepentant war criminal, and his novels found to have embodied a kind of esoteric apologia for Nazi ideology. Then we would at least have solid, straightforward grounds on which to force a re-reading of his work. But hypocrisy, involving a contradiction between private life and public persona, is a trickier quality to assess.

Where a political and moral analysis is concerned, whether filtered through literature or otherwise, it is supposed to be the merit of the arguments presented, rather than the stature and record of the author presenting them, which recommend them for public debate and political action. The truth and utility of Grass's public analyses (in both fictional and non-fictional guises) of post-war Germany should not in principle be altered by his moral qualities as a private individual.

That said, the trouble with Grass's case is that just as it is impossible to disentangle his literary from his political legacy - his works of fiction, from the Tin Drum to 2003's controversial Crabwalk, are both driven by and intent on driving towards a particular moral and political vision of Germany - so too is it impossible to separate Grass' works from their author. In Germany, at least, having made himself so visible as the author of his works, it seems impossible that the damage done to his personal reputation will not leave deep scars on his books.

In an international environment, though, the case is somewhat different. Further removed from the struggle that has marked the last 60 years of German history, the sense of betrayal is bound to be less keen for those whose relation to Grass's work is a literary and aesthetic one. In a climate where it nowadays seems possible - if not uncontroversial - to admire the films of Leni Riefenstahl, the belated revelation of, as it were, "yet another" shameful episode in the wartime past of a prominent creative personality seems unlikely to make any lasting difference. Moreover, besides its purely literary merit, for non-German readers much of the value of Grass's work has been in the powerful access it provides to the complex morality and psychology of post-war Germany. Given that hypocrisy of precisely the kind now on display by their author is portrayed in his works as having been such an important feature of this psychology, whether you see the books through their author, or the author through his books doesn't seem to make much difference.

It is also arguable that having the kind of growing psychological burden that Grass must have had to carry all these years may in many ways have acted as a kind of stimulus to sustained activity and effort in what may be independently judged as the right direction. His response to the current situation - "My silence all these years was one of the reasons I had to write [my autobiography]" - seems uniformly weak if nonetheless highly plausible, but, as with Conrad's Lord Jim, those with a guilty past are often the most zealous when it comes to repairing the present. If Grass's silence is also partly what spurred him on, then the route to condemnation is less easy.

Hypocrisy is always ugly, but ugliness is no less important to literature than beauty. Grass's crime is to have betrayed those whose spokesman he has sought to be. For those of us lucky enough not to have required his services in this respect, he remains as powerful and as interesting a writer as before.